Outside of his KO loss to Bute, Andrade was known for taking bombs unphased. This is active fighters, right?
Marquez' chin isn't great actually IMO, he's been put down often and hurt. He just has great recuperative abilities so he recovers his sense quickly. Also he's a smart fighter. Also massive heart.
Oli McCall is still active. Anyone who can take flush right hands to the chin from Lennox Lewis without budging deserves to be on that list. Oli McCall has the best chin in boxing, maybe not only of this era. In that regard, Vitali has a great chin too.
I wouldn't have Mosley there personally. I think he has shown more reactions to punches than it first may appear. Forrest made him weary for two fights (he IS a very good puncher though) and Winky made him a bit shaky. His inability to adapt isn't entirely because of low ring IQ and susceptibility to a good jab IMO. Look at the 12th round of their first fight - it wasn't only due to tiredness. Mayweather hurt him repeatedly. Now, I know Mayweather's power is actually very underrated and Pac may find that out in their fight, but Mosley's reactions I did not like. And Margarito barely hit him with any full-steam punches; it was mostly volume. I'll give you DLH. The way he took some of the left hooks was absolutely astonishing. I was thinking "now, he must be hurt...". But he wasn't! A very good chin but not amongst the very best. Vitali was hurt against Sanders and briefly stunned against Lewis but he recovered quickly in both cases. Briggs didn't hit him but Vitali belongs here I feel. Hopkins is a good mention. The only time I've seen him truly hurt was vs Mercado some 16 yeras ago. His defense has deteriorated and Pascal hit him flush a lot more than I expected. Hopkins took these very well as well as Jones's hard punches in 1993. Rico, staying on your feet certainly isn't the only way to measure a chin. Toney's knockdown vs Peter was an off-balance one. Just Look at the left hand he took against Jirov in the last 30 seconds or so. He actually made, for him, a very uncharacteristic mistake of walking into a flush punch against the ropes. Thing is - he just stood there and some seconds later knocked Jirov down!! McCallum and Peter (size advantage) are also good punchers and Toney showed no effects. Of course he should be mentioned! Margarito tops for me. Some of the punches Cintron hit him with made ME hurt. Look at the left hand from Cotto he walked right into in the closing seconds of the... second round I think. And I've very rarely seen a fighter get so pummeled for nine rounds as in the Mosley fight. Unlike the fight against the retreating Cotto, Mosley went forward and got all the power in his shots and Margarito walked through it about 100 times. Sick... Isn't that a good chin for you? I totally agree with Tommy's post btw. I would put Mosley out and put in the Pacman. He belongs without any doubt for me. P4P he might be the most proven actually. Some examples: Uppercut vs middleweight Margo in the eighth round, underrated precision puncher Marquez flush shots for 24 rounds, Cotto's left hooks to the temple mainly in the second round and flush Morales right hands in their grueling first fight. I mean - he has to be mentioned! No one alse, except maybe Toney, has proven his chin at so many weights. Difference being that Pac gets hit reasonably much for a top fighter whereas Toney is a hard one to nail flush. Without his chin Pac would be toast against Cotto and Margo and I remember everyone questioning whether he could take Hatton's punches - let alone a WW punch! Adamek was nearly out against modest pucnhing USS, briefly stunned against Banks and hurt by Arreola and grant. A warrior, sure, but not quite up there. Honourable mentions: Agbeko, Mosley, Kessler, Froch (perhaps not but I'll put him in in lack of others). Lebedev has a solid one too I feel but let's wait to properly judge.
I forgot about Duddy! He can sure take a punch, but he looked like he was on his way out against Chavez Jr. The bombs he took from Campas and Eastmann were impressive.
Is Gerry Penalosa still active? Neither Ponce de Leon or Juanma Lopez were able to knock him down, and they're both very big punchers.